that is exactly what I was going to say. I personally believe there is a correlation between drug use and early onset schizophrenia in young men too. It may not be causation but there is a correlation from what I have seen several times.
Schizophrenics also try to self-medicate with drugs; it’s an chicken-and-egg situation, but it’s pretty clear that there’s an existing brain chemistry abnormality before the drug use.
Which is one of the reasons you can "miss" the onset.
The pro-MJ crowd want to make more MJ available so that all these schizophrenia susceptible individuals can wig out now rather than later.
There also are suggestions that people may be self-medicating — smoking pot because of mental illness, rather than becoming mentally ill because of drug use.
I have a neighbor who has schizophrenia. He told me that he developed it after years of smoking pot. His meds weren’t working for him a few months ago and I had to call an ambulence for him because he was standing out side his duplex wearing only a T-shirt and doing other weird things.